Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 252321
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
721 PM EDT WED MAY 25 2016

.SYNOPSIS...
High pressure weakens and moves farther offshore through Thursday.
Meanwhile a weak cold front moves in Thursday. This front will back
north as a warm front Thursday Night. A Bermuda high will
then dominate through the weekend, bringing summertime warmth as
a series of weak upper level disturbances touch off convection
each afternoon and early evening. A back door cold front will
approach Sunday into Sunday night, then retreat back north early
next week as a weak front slowly approaches from the west and a
broad area of low pressure slowly approaches from the south.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Updated the forecast to include a low chc of pops for interior srn
ct. An area of showers was approaching from the nw and timed to
reach northern new london around 23z. The showers are currently
showing signs of weakening so it may dissipate before reaching the
cwa. Also increased cloud cover across eastern portions of the
forecast area for a few hours this eve based on latest sat
imagery and trends. Minor adjustments made to t/td and winds as
well based on latest obs and trends. Temps were several degrees
warmer than forecast at 22z and should be slow to decrease early
this eve.

Otherwise...just a few clouds with mainly clear skies to start
out tonight. Sea breeze circulations will eventually weaken and
gusts will subside during the evening.

Overall, ridging takes place aloft. However, looking at a larger
scale, the ridge will become more flat with a series of shortwaves
riding along the top of it as diagnosed by positive vorticity
advection. With high pressure shifting farther offshore at the
surface tonight, subsidence will be lessening with time. As a
result, cloud cover will be increasing late tonight. Used a blend
of mav/met for lows with manual adjustments up near some coastal
rural locations due to partial onshore flow.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
For Thursday, some slight ridging takes place aloft with overall the
ridge still exhibiting a rather flat structure. The models are
pointing to a relatively stronger shortwave that will be riding
along the top of the ridge, arriving into western portions of the
region by Thursday Evening. At the surface, high pressure will shift
farther offshore and weaken. A cold front moves across during the
day and weakens as it does so. This will bring some extra clouds
during the day. With the weak pressure gradient, sea breezes set up
sooner with a more southerly component. This will keep coastal
location temperatures a few degrees cooler compared to the previous
day while interior locations will be nearly the same temperatures as
the previous day.

Weather will start out dry with enough subsidence of residual ridging
and then with the approach of the shortwave as well as increasing
instability, some showers and thunderstorms will be possible late in
the day and evening. The subsidence will still be enough to prevent
much in the way of any convection from developing. With the approach
of the shortwave, places north and west of NYC will have a slight
chance of showers and thunderstorms late in the day since those
locations will be relatively closer to the shortwave.

For Thursday Night, the shortwave moves across while at the surface,
the weak cold front will move back north as a warm front. The
presence of the frontal boundary and the increased positive
vorticity advection aloft will allow for a relatively greater chance
of showers. Convection with the lack of CAPE will be minimal with
any coverage being isolated.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Earlier forecast reasoning still holds, with summertime warmth
through the weekend as longwave upper ridging moves across. A warm
front will clear the entire area Fri morning, and with H8 temps near
16C and H5-10 thicknesses near 570 dm, high temps are likely to
reach the lower 90s both Fri/Sat NW of NYC, with 80s elsewhere
except for the south shore of eastern Long Island. There is a good
chance for late day tstms from NYC north/west as a mid level
disturbance interacts with a lee trough. Wind fields are not
particularly strong aloft, but deep layer shear might still support
a few strong to locally severe storms. Any late convection on
Saturday will be isolated in nature and tied more to differential
heating in/near the higher terrain.

The northern stream disturbance moving across eastern Canada has
trended faster, which means any associated back door cold front may
not make it into the area at all, or only into eastern CT/Long
Island. So Sunday will still be a warm day, though not quite as warm
as the previous two days. Once again looking mainly at scattered
late day convection tied either to the front or to a lee trough NW
of NYC, and as another weak mid level vort max approaches from the
west.

Monday should be cooler, with more cloud cover as shortwave energy
Atlantic moisture ride up the coast, well in advance of a low off
the Southeast coast, and on the back side of the retreating offshore
ridging. Once this passes, we should return to warm weather and
chances for sct mainly inland late day convection as another upper
ridge moves in from the west.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
High pressure builds to the south tonight and Thursday.

VFR forecast.

Lingering sea breezes lighten, otherwise winds lighten from the
west/southwest overnight.

Light winds in the morning become south around 10 kt. Sea breezes
are expected by afternoon, sooner across CT terminals.

 ...NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component
forecasts, can be found at: http:/www.weather.gov/zny/n90

KJFK TAF Comments: Winds lighten this evening, with no
unscheduled amendments expected. Sea breeze Thursday, and winds
increase to 10 to 15 kts. Timing of sea breeze could be off an
hour or two.

KLGA TAF Comments: Winds lighten this evening, with no
unscheduled amendments expected. Sea breeze Thursday, and winds
increase to 10 to 15 kts. Timing of sea breeze could be off an
hour or two.

KEWR TAF Comments: Winds lighten this evening, with no
unscheduled amendments expected. Sea breeze expected Thursday as
light SW winds turn to the S/SE. Timing of Seabreeze could be off
an hour or two.

KTEB TAF Comments: Winds lighten this evening, with no
unscheduled amendments expected. Sea breeze expected Thursday as
light SW winds turn to the S. Timing of Seabreeze could be off an
hour or two.

KHPN TAF Comments: No unscheduled amendments expected this
evening. Sea breeze expected Thursday as light SW winds turn to
the S. Timing of Seabreeze could be off an hour or two.

KISP TAF Comments: No unscheduled amendments expected this evening.
Sea breeze Thursday, and winds increase to 10 to 15 kts. Timing of
sea breeze could be off an hour or two.

.OUTLOOK FOR 00Z Friday through Monday...
.Thursday night through Friday morning...Mainly VFR but sub-VFR
possible in showers/evening thunderstorms.
.Friday through Friday night...Mainly VFR, but sub-VFR possible in
isolated showers and evening thunderstorms.
.Saturday...Mainly VFR. Isolated showers and thunderstorms north
of NYC/Long Island.
.Sunday...Sub-VFR possible in afternoon showers and thunderstorms.
.Monday...Sub-VFR possible in showers and thunderstorms.

&&

.MARINE...
With the pressure gradient overall remaining rather weak...the seas
and wind gusts will stay below SCA criteria through Thursday
Night.

S-SW flow increasing to near 20 kt may bring a brief period of 5-ft
seas to the western ocean waters late day Fri into Fri evening.
Otherwise, expect quiet winds/waves outside of any potential
thunderstorms.

&&

.HYDROLOGY...
No significant widespread precipitation expected through Thursday
Night.

Local minor flood impacts from heavier showers/tstms are possible
with any late day convection, on Friday and Sunday, mainly NW of
NYC. Heavy rain may also be possible on Monday with an upper level
disturbance and Atlantic moisture riding up the coast, but timing
and location are uncertain, and at this time looks likely to pass
just offshore Long Island.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$



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